Herbal supplement use and blood lead levels of United States adults.

BACKGROUND: Some herbal supplements may contain lead.

OBJECTIVE: To examine whether use of specific herbal dietary supplements during the last 30 days is associated with blood lead levels in US men and women.

DESIGN: Cross-sectional analysis.

STUDY POPULATION: NHANES participants from 1999-2004, a representative sample of the civilian non-institutionalized US population.

MEASUREMENTS: Lead was measured in blood. Associations between lead and self-reported supplement use were estimated using multivariable regression weighted to account for NHANES sampling. Herbal supplements investigated were those previously reported to contain high heavy metal content: Ayurvedic or traditional Chinese medicine herbs, echinacea, ginkgo, ginseng, St. John's wort, and "other" herbs (specifically, kava, valerian, black cohosh, bee pollen, and nettle).

MAIN RESULTS: Among 6,712 women > or =20 years, those using herbal supplements had lead levels that were 10% higher than non-users (95% CI 3%-17%, p = 0.005). Women using Ayurvedic or traditional Chinese medicine herbs, St. John's wort, and "other" herbs had lead levels 24% (95% CI 5%-45%, p = 0.01), 23% (95% CI 4%-46%), p = 0.02), and 21% (95% CI 2%-44%, p = 0.03) higher, respectively, than non-users. No significant associations were observed between herb use and lead levels among men (n = 6,095). Among reproductive-aged women (16-45 years), herbal supplement users had lead levels 20% higher than non-users (95% CI 5%-34%, p = 0.008). In contrast, garlic and other dietary supplements were not associated with higher lead levels.

CONCLUSION: Use of specific herbal supplements is associated with higher blood lead levels among women. Our data suggest testing guidelines for herbal supplements and regulations limiting lead in supplements are needed.